STP982: Crack Closure Behavior of Surface Cracks Under Pure Bending

    Foroughi, R
    Research assistant and research fellow, Imperial College, London,

    Radon, JC
    Research assistant and research fellow, Imperial College, London,

    Pages: 10    Published: Jan 1988


    Abstract

    By the application of a compliance technique the fatigue crack closure behavior of surface cracks in British Standard or Low Alloy Steels, Composition and Properties (BS) 4360-50D structural steel was investigated under pure bending. Crack closure at the vicinity of surface intersection points was monitored by use of an Elber type gage, whereas the overall closure behavior was determined by means of a standard clip gage situated at the notch mouth. Under constant amplitude loading the crack opening load was larger around the surface intersection points than the overall opening load. For the range of ΔK that was considered, Kop increased with Kmax and the variation was dependent on the applied stress ratio. A comparison of the results of this study with those in the literature showed that the closure response of surface cracks under bending was less significant than that observed from the through thickness crack geometries. The closure parameter U showed an increasing trend with ΔK. However, for a low stress ratio the influence of closure was much more pronounced at small ΔK values. Presentation of the crack growth data of the surface intersection points in terms of ΔKeff produced well correlated data without any mean stress effect being observed in the mid-range regime.

    Keywords:

    crack closure, surface cracks, bending fatigue, stress ratio, crack growth


    Paper ID: STP27214S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP27214S


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